1. Field of the Invention
The present invention relates to door locks and in particular to controlling operation of door locks wirelessly by authorized users.
2. Description of Related Art
Multiple factors are driving the adoption of cell phones as a method for opening door locks. These factors include low power and secure wireless technologies like Bluetooth 4.0, universal adoption of Bluetooth by cell phone manufacturers, and widespread consumer use of smart phones.
In the desired operation, a user approaches the front door of the home or apartment, the phone and lock identify that the user is in close proximity and located on the exterior of the door before allowing entry, the lock unlocks and the user simply rotates the actuating lever or knob of the lock and enters the dwelling. Once inside, it is desirable if the lock and phone do not inadvertently unlock the door. All of these steps would ideally occur seamlessly to the user, e.g., the user does not need to interact with the phone or the lock.
Unlike NFC (near field communication) technology, where a phone needs to be presented to a door lock like an RFID credential, Bluetooth technology can function at a range of over 30 m (100 ft.). Although this is convenient for a user because the phone and lock can communicate without user interaction (e.g. the phone can be left in your pocket), this also is a major problem because the phone might unlock a door in an unintended way. One example of an unintended circumstance is when a user pulls into a parking space outside their apartment and the front door unlocks within the building. Considering that it may take 10 minutes to get to the opening, this is an unacceptable condition. Another example of an unintended circumstance is when a user carries the phone around inside their apartment and the front door unlocks in an unexpected way. This might happen if the user moves out of range or resets the phone and the connection is later restored.
Since Bluetooth is a wireless technology, it can pass through walls, and therefore, it is difficult to determine the location of a phone. Recent industry attempts at solutions include attempting to shield the Bluetooth antenna to block signals from inside a building or residence, and attempting to detect differences in Bluetooth signal strength by placing additional wireless sensors inside the building or residence. These attempts at solving the problem require cumbersome installation issues and extra expense.